The present invention relates to a method of heating molten steel by an arc process, wherein an arc is formed between molten steel and electrodes dipped in slag on molten steel contained in a ladle.
By using an arc process to heat molten steel after converter refining, the converter tap temperature of the molten steel can be decreased, thereby leading to a decrease in the required amounts of converter refractory and auxiliary materials. The yield of molten steel tapped from the converter can thus be increased.
In order to perform the arc process, molten steel is tapped from a converter into a ladle, and carbon electrodes are dipped into slag on the molten steel. An arc is formed between the molten steel and each electrode while the electrodes are surrounded by the slag.
If nitrogen gas is, however, present in the ladle during arc heating, it is absorbed by the molten steel, increasing the nitrogen concentration [N] in molten steel, thus causing the nitrogen pickup phenomenon. In order to prevent this nitrogen pickup phenomenon, argon gas is blown into the ladle or into work holes into the cover of a conventional ladle, thereby sealing the molten steel off from any nitrogen gas present.
Using this conventional sealing method, however, it takes about an hour to seal the molten steel off from the nitrogen gas. In addition, in order to completely prevent the nitrogen pickup phenomenon, the argon gas must be provided at a high flow rate, e.g., of about 300 Nm.sup.3 /h. Furthermore, sealing degrades the efficiency of the arc process, and the large amount of argon gas required increases the total process cost.